Leonard waldo



(No Model.) 2Sheets -Sheet 1.

' L. .W'ALDO & IF. A. GOOOH.

PROCESS OF REDUCING ALUMINIUM. No. 527,846. Patented Oct. 23, 1894.

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L. WALDO & F. A. GOOOH.

PROCESS OF REDUCING ALUMINIUM.

No. 527,846 Patented Oct. 23, 1894. v

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UNITED STATES PATENT OFFICE.-

LEONARD WALDO, OF BRIDGEPORT, AND FRANK A. GOOCH, OF NEW HAVEN,CONNECTICUT; SAID WALDO' ASSIGNOR TO THE WALDO FOUNDRY, OF NEW JERSEY.

.PROCESS OF REDUCING ALUMINIUM.

. SPECIFICATION forming part of Letters Patent No. 527,846, datedOctober 23, 1894.

Original application filed September 1, 1893, Serial No.484,561. Dividedand this application filed March 23, 1894. Serial No. 504,763. ospecimens.)

.To all whom it may concern.-

Be it known that we, LEONARD WALDO, residing at Bridgeport, in thecounty of Fairfield, and FRANK A. GOOCH, residing at New Haven, in thecounty of New Haven, State of Connecticut, have invented certain new andusefullmprovements in Processes of Reducing Aluminium; and we do herebydeclare the following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which itappertains to make and use the same, this being a divisional applicationof the application filed by us September 1, 1893, Serial No. 484,561.

The invention described herein relates to processes for the reduction ofaluminium from its compounds by the electrolysis of a suitable fusedmass containing such compounds.

In general terms, our invention comprises an improved process forreducing aluminium from its compounds, which consists in passing anelectric current through a suitable fused bath containinga suitablehalogen compound of aluminium, thereby electrolyzing the bath, and inintroducing hydrogen into the bath. The compound of aluminium usedshould be one which will fuse at a temperature and under conditionswhich shall be practically attainable.

In practice we find that the halogen compounds of aluminium which-aremost suitable and best adapted to .be used in our pro cess are thechloride of aluminium and the fluoride of aluminium. By the introductionof hydrogen into the bath in the manner above described, a more uniformintermixture of the ingredients of the bath is secured. The surface ofthe molten mass is protected from atmospheric action when the hydrogenis used in some excess. The anodes are protected from the corrosiveaction of the halogens set free by the electrolysis of the bath, andsuch.

free halogens are converted into a more manageable form.

For convenience, we describe our invention with special reference to thereduction of aluminium from its chloride, it being understood, however,that our invention is also applicable to other compounds of aluminium.In the accompanying drawings, which are hereby made a part of thisspecification, is

Fig. 2 represents a sectional view of a n 1odi fied form of apparatusemployed by us.

Similar letters refer to similarparts throughout the drawings.

F is a furnace having a fire box f, and opening f in the top of thefurnace, into which is set a tapering crucible A, the same beingsupported by the sides of the opening f.

The construction of the crucible and the arrangement of the electrodesand conductors are hereinafter fully described.

T is a tank from which the hydrogen is supplied through the tube H, thesupply being regulated by the cook 25. s s are binding posts for theconductors N, P.

The construction and arrangement of other parts of the apparatusemployed are hereinafter fully described.

In the practice of our invention, so far as it relates to the reductionof aluminium from its chloride, we preferably prepare a bath by fusingin a suitable tank or crucible A, and in proper proportions, thechloride of aluminium and the chloride of an alkaline metal,

(preferably sodium,) or of an alkaline earth metal, with the fluoride ofaluminium and the fluoride of SOdlllID. A convenient Way to form asuitable bath is to combine the chloride of aluminium andthe chloride ofmagnesium with the mineral cryolite. We find it of advantage to add tothe combination just named acertain proportion of chloride of sodium,which .has the elfect of making the bath more liquid. These ingredients,

are preferably mingled together in the following proportions: cryolite,fifty-five parts; chloride of aluminium, twelve parts; chloride ofmagnesium, five parts; chloride of sodium, twenty eight parts; but theproportions above given are variable serviceably within considerablelimits without materially affecting the operation or function of thebath, as, in fact, any proportions which may be found suitable may beemployed,

The reason for employing cryolite or the fluorides of aluminium andsodium in the bath, is the well known fact that, when they are presentand reduction by the action of the electric current takes place, thealuminium melts and flows to globules; while, when the bath containsonly the chlorides named, the aluminium is obtained in the form of apowder, which has to be further treated before it can be madecommercially available.

The crucible A, preferably employed by us in the operation of ourinvention, consists of a tank of iron lined with compacted carbon. Thecarbon lining L of this tank serves as the-cathode, the iron of the tankbeing connected by the conductorN with the negative pole of a dynamoelectric machine or other suitable source of electricity 0. The anode Cis a detached carbon electrode partially immersed in the bath B; andconnected in the following manner with the source of electricity: Wepreferably suspend the anode from an iron bar D raised above thecrucible and restingon wood en supports E E. The bar D is connected bythe conductor 1? to the positive pole of the source of electricity.

If desired, the cathode may also be formed of a detached carbon,suspended in a similar way to that just described for the anode, orotherwise supported, and partially immersed in the bath B. If desired, anumber of separate carbons may be used to form the electrodes as shownin Fig. 2, Where C 0' C C and C all suspended from the bar D,collectively form the anode. The relative superficial areas of theelectrodes in any particular case are adjusted so as to secure thegreatest economy in action. In place of a carbon anode, an anode of anyother suitable material, as of platinum, may be used. The bath may befused, and the fusion may be maintained by the application of heat fromany suitable source, as from a furnace F. The temperature required tofuse our preferred bath is that of a dull red heat. We may also fuse theingredients of the bath in a separate apparatus and introduce the samein a molten condition into the bath at the beginning of the process, thefusion being thereafter maintained in any suitable way. When theelectric current is passed through the bath and electrolysis takesplace, aluminium is deposited at the cathode and the halogens (chieflychlorine) are liberated at the anode. It is well known that these gases,in a free state, are highly noxious to health. On this account, and forthe further reason that they attack and quickly destroy the positiveelectrode in the apparatus used in any process similar to the onedescribed, their escape in a free state would render such processcommercially useless. To obviate these difficulties, and to accom plishother desirable results, we introduce into the bath hydrogen. Thehydrogen is preferably delivered in a substantially continuous supplyunderneath the surface of the fused mass in near proximity to or throughthe anode. In the latter case, a longitudinally perforated carbon rod 0is preferably employed for the anode, and the gas is passed through thesame as through a pipe, the gas being supplied through a tube Hconnecting with the upper end of the anode O, which may project abovethe barD. The hydrogen may also if preferred be conducted through aseparate pipe as the pipe Min Fig. 2. When the halogen elements areliberated by the electrolysis of the bath, they combine instantly withthe free hydrogen and escape at the anode in the form of hydrochloricacid or hydrofluoric acid, chiefly the former. These gases, in thequantities evolved in our process, are easily controlled and disposedof, without injury to apparatus or workmen, by appropriate meansexternal to the bath, as by the use of a fine K, having a strong draft,and provided with a hood J, projecting over i the crucible A; (see Fig.1;) or cloths orother absorbent media, saturated with water, may besuspended over the crucible, the escaping gases being taken up by thewater, whose power of acting as a solvent for hydrochloric acid andhydrofluoric acid is well known. Such an arrangement is shown in Fig. 2,where a represents an endless band or apron of cloth or other suitablefabric, passing over drums m m attached to shafts b, h. The shaft 1)revolves in journal boxes e and is supported in any suitable manner, asbya strip 6 suspended from the ceiling. The shaft 7t revolves in boxes eformed on the edges of the trough 7c. The shafts and band or apron a arekept in revolution in the direc tion indicated by the arrows by powerfrom any suitable source transmitted by the belt (Z, passing over thepulley c, which is rigidly attached to the shaft 1). The shaft 1) ishung somewhat higher that the shaft h. The drum 'm on shaft h runs closeto or under the surface of Water w contained in a shallow pan or trough70, having suitable support I. The band or apron a being inclined passesthrough the water to on the lower side of the drum m 'and is thus keptsaturated with water. Thus saturated it passes continuously over thecrucible.

WVe do not claim the particular arrangement of devices just described,not regarding it as novel, nor do we confine ourselves to the particulardevices shown, since any other suitable means external to the bath mightbe employed for disposing of the escaping gases.

W'e preferably supply hydrogen to the bath in excess of the amountrequired to combine protecting the surface of the molten mass fromatmospheric action.

In the practical operation of our invention,

where we use the suggested bath composed of the chloride of aluminiumand the chloride of magnesium and the fluorides of aluminium and sodium,with or without the chloride-of sodium, we have found that we obtain atthe anode hydrochloric acid almost exclusively, with very little traceof fluorine. This shows that the aluminium deposited at the cathode isderived chiefly from the chloride of aluminium in the bath; and we havefound that, by the occasional addition of chloride of aluminium (Al Ulin sufficient quantities, the bath will be replenished, and the processwill be a substantially continuous one during a considerable period oftime. An excess of the chloride of aluminium produces no injuriouseffect, as it is gradually utilized in the subsequent operation of theprocess.

We have hereinbefore spoken of fluorine being set free, though we areaware that it is considered very difficult to isolate this element. We,however, use the term fluorine merely for convenience, meaning therebyto include not only free fluorine, if any be liberated, but also anycompound thereof, which might be set free at the anode, if hydrogen werenot supplied to the bath in the process.

As before stated, the aluminium is deposited at the cathode, Where itmelts forming globules, which, when the suggested bath'whose proportionsare hereinbefore stated is employed, gather at the bottom of the bath,the aluminium having'a higher specific gravity than the fused bath. Thealuminium may then be removed in any suitable manner, as by means of aladle lined and covered with carbon, or by drawing it off at the bottomthrough a suitable opening; or the bath may be poured out, and, afterbeing cooled, the aluminium may be picked out.

In case a bath should be used whose specific gravity is higher than thatof aluminium, the aluminium would rise to the top,'where it could beeasily removed.

In the process herein described, we use an electric current of suitablylow electro-motive force, usually of from four to ten volts; but thevoltage of the current employed will depend on the form and size of theelectrodes as well as on the composition of the bath, it being onlynecessary to have a voltage sufficient to decompose electrolytically thecompound of aluminium in the bath under all the existing conditions ofresistance, and of chemical constitution The electric current which weemploy in our process, and which is herein referred to as being passedthrough the bath, is employed solely for purposes of electrolysis.

The excess of The hydrogen may in the first instance be I We are awarethat hydrogen has been employed heretofore in processes for reducingaluminium, either as the sole agent or as an auxiliary agent inaccomplishing the reduction of the metal from the aluminium compoundsused. In the process herein described, we do not employ hydrogen as anagent in such reduction, nor do we in this application claim any processin which hydrogen is so employed. The objects of introducing hydrogeninto the bath in our improved process herein described are, as beforestated, to secure a more uniform intermixture of the ingredients of thebath, to protect the surface of the molten mass from atmospheric action,to protect the anodes V from the corrosive action of the halogens setfree by the electrolysis of the bath, and to convert such free halogensinto a more manageable form.

We do not herein specifically claim those forms of the process hereindescribed which are particularly set forth and claimed in ourapplication filed September 1, 1893, Serial No. 484,5 61, of which thisapplication is a division.

It being possible to form a number of different baths to any of whichour invention would be applicable, we do not limit our invention to theuse of any particular bath which hasbeen described herein.

Having described our invention, what we claim, and desire to secure byLetters Patent, 1s-

1. As an improvement in the art of manufacturing aluminium, the hereindescribed process, which consists in forming a bath by fusing thechloride of aluminium and the chloride of an alkaline earth metal withthe fluoride of aluminium and the fluoride of sodium, passing anelectric current of suitably low voltage through the fused mass, therebyelectrolyzing the same, and supplying hydrogen to the bath,substantially as and for the purposes set forth.

2. As an improvement in the art of manufacturing aluminium, the hereindescribed process which consists in forming a bath by fusing togetherthe chloride of aluminium and the chloride of magnesium with thefluorides of aluminium and sodium, passing an electric current ofsuitably low voltage through the fused mass, thereby electrolyzing thesame,

and supplying hydrogen to the bath, substan Q fused mass, therebyelectrolyzing the same, and supplying hydrogen to the bath, substau: andsupplying hydrogen to the bath,substantially as and for the purposes setforth. tially as and for the purposes set forth.

4. As an improvement in the art of iuanu- 5 t'acturing aluminium, theherein described m process, which consists in forming a bath by\Vitnesses to signature of Leonard \Valdo:

fusing together the chloridesof aluminium, FRANK L. CRAWFORD,

magnesium and sodium and the fluorides of MARION FOWLER.

aluminium and sodium, passing an electric Witnesses to signature ofFrank A. Gooch: 10 current of suitably low voltage through the SARAH W.GOOGH,

fused mass, thereby eleetrolyzing the same, INA B. MORRISON.

